U.S. patent application number 14/366732 was filed with the patent office on 2014-11-27 for rotor.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. The applicant listed for this patent is Masahiro Nigo, Kazuchika Tsuchida. Invention is credited to Masahiro Nigo, Kazuchika Tsuchida.
Application Number | 20140346911 14/366732 |
Document ID | / |
Family ID | 48696483 |
Filed Date | 2014-11-27 |
United States Patent
Application |
20140346911 |
Kind Code |
A1 |
Tsuchida; Kazuchika ; et
al. |
November 27, 2014 |
ROTOR
Abstract
A rotor includes a rotor iron core in which magnet insertion
holes that are arrayed in a radial direction so as to be convex
toward an inner peripheral side are provided for each magnetic
pole, and in which the magnet insertion holes are arranged in a
circumferential direction according to the number of magnetic
poles, and flat-shaped permanent magnets that are inserted
respectively in the magnet insertion holes, wherein the magnet
insertion holes, which are arranged on an innermost peripheral side
and adjacent to each other in a circumferential direction are
provided in such a manner that the width of the magnet insertion
hole gradually becomes larger toward the inner peripheral side such
that the width of the iron core between the adjacent magnet
insertion holes in a circumferential direction is constant in a
radial direction.
Inventors: |
Tsuchida; Kazuchika; (Tokyo,
JP) ; Nigo; Masahiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tsuchida; Kazuchika
Nigo; Masahiro |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
48696483 |
Appl. No.: |
14/366732 |
Filed: |
December 26, 2011 |
PCT Filed: |
December 26, 2011 |
PCT NO: |
PCT/JP2011/080054 |
371 Date: |
June 19, 2014 |
Current U.S.
Class: |
310/156.53 |
Current CPC
Class: |
H02K 1/246 20130101;
H02K 1/2766 20130101; H02K 1/276 20130101; H02K 2213/03
20130101 |
Class at
Publication: |
310/156.53 |
International
Class: |
H02K 1/27 20060101
H02K001/27; H02K 1/24 20060101 H02K001/24 |
Claims
1. A rotor comprising: a rotor iron core in which a multi-layered
magnet insertion holes that are arrayed in a radial direction so as
to be convex toward an inner peripheral side are provided for each
magnetic pole, and in which the multi-layered magnet insertion
holes are arranged in a circumferential direction according to a
number of magnetic poles; and flat-shaped permanent magnets, each
of which is inserted into the respective magnet insertion holes,
wherein the width of the iron core between the adjacent magnet
insertion holes, which are arranged on an innermost peripheral side
and adjacent to each other in the circumferential direction, is
constant, and the width of each of the holes gradually becomes
larger toward the inner peripheral side.
2. The rotor according to claim 1, wherein each of the magnet
insertion holes arranged on the innermost peripheral side
comprises: a main portion that extends with a constant width in a
direction perpendicular to an array direction of the multi-layered
magnet insertion holes, and end portions that communicate with
respective sides of the main portion and extend toward an outer
peripheral side at an obtuse angle with respect to an extending
direction of the main portion.
3. The rotor according to claim 1, wherein among the multi-layered
magnet insertion holes, a rare-earth magnet is inserted into each
of the magnet insertion holes on the outermost peripheral side, and
a ferrite magnet is inserted into each of the magnet insertion
holes on the innermost peripheral side.
4. The rotor according to claim 3, wherein the width of the
rare-earth magnet in the radial direction is smaller than the width
of the ferrite magnet in the radial direction.
5. The rotor according to claim 2, wherein each of the magnet
insertion holes arranged on the outermost peripheral side
comprises: a main portion that extends with a constant width in a
direction perpendicular to an array direction of the multi-layered
magnet insertion holes, and end portions that communicate with
respective sides of the main portion and extend toward an outer
peripheral side at an obtuse angle with respect to an extending
direction of the main portion.
6. The rotor according to claim 5, wherein the widths of the iron
core at portions between the end portions of the magnet insertion
holes arranged on the outermost peripheral side and the end
portions of the magnet insertion holes arranged on the innermost
peripheral side are both constant.
7. A motor equipped with the rotor as disclosed in claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a U.S. national stage application of
International Patent Application No. PCT/JP2011/080054 filed on
Dec. 26, 2011.
TECHNICAL FIELD
[0002] The present invention relates to a rotor of a rotary
electric machine.
BACKGROUND
[0003] Patent Literature 1 discloses a synchronous reluctance motor
that includes two layers of permanent magnets in a radial direction
in the rotor, and that has a configuration in which the total
amount of magnetic flux in the permanent magnet on the outer
peripheral side is designed to be larger than or substantially
equal to the total amount of magnetic flux in the permanent magnet
on the inner peripheral side.
PATENT LITERATURE
[0004] Patent Literature 1: Japanese Patent Application Laid-open
No. 2002-272031
[0005] Because a reluctance motor uses reluctance torque in
addition to magnet torque, it is desirable for a magnet insertion
hole to have a shape that increases the reluctance torque. Although
in Patent Literature 1, there are descriptions indicating that a
rare-earth magnet is inserted on the outer peripheral side, and a
ferrite magnet is inserted on the inner peripheral side, a shape of
the magnet insertion hole that can increase the reluctance torque
is not mentioned.
[0006] The present invention has been achieved to solve the above
problems, and an object of the present invention is to provide a
rotor that includes a magnet insertion hole having a shape that
increases the reluctance torque and makes it possible to obtain a
high output.
[0007] in order to solve the aforementioned problems, a rotor
according to one aspect of the present invention is constructed in
such a manner that it includes: a rotor iron core in which a
multi-layered magnet insertion holes that are arrayed in a radial
direction so as to be convex toward an inner peripheral side are
provided for each magnetic pole, and in which the multi-layered
magnet insertion holes are arranged in a circumferential direction
according to a number of magnetic poles; and flat-shaped permanent
magnets, each of which is inserted into the respective magnet
insertion holes, wherein the magnet insertion holes, which are
arranged on an innermost peripheral side and adjacent to each other
in the circumferential direction, are provided in such a manner
that the width of each holes gradually becomes larger toward the
inner peripheral side so that the width of an iron core between the
adjacent magnet insertion holes in the circumferential direction is
constant in the radial direction.
[0008] The present invention can increase reluctance torque and
obtain a high output.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a plan view of the shape of a rotor core 1a (a
rotor iron core) of a rotor 1 according to an embodiment.
[0010] FIG. 2 is a partially enlarged view of FIG. 1.
[0011] FIG. 3 is a plan view of a configuration of the rotor 1
according to the embodiment.
[0012] FIG. 4 is a partially enlarged view of FIG. 3.
[0013] FIG. 5 is a plan view of a configuration of a rotor 100
according to a comparative example.
[0014] FIG. 6 is a partially enlarged view of FIG. 5.
[0015] FIG. 7 is a partially enlarged view of FIG. 5.
[0016] FIG. 8 is a partially enlarged view of FIG. 5.
DETAILED DESCRIPTION
[0017] Exemplary embodiments of a rotor according to the present
invention will be explained below in detail with reference to the
accompanying drawings. The present invention is not limited to
these embodiments.
Embodiment
[0018] A motor rotor according to the present embodiment is
explained below. FIG. 1 is a plan view of a shape of a rotor core
1a (a rotor iron core) of a rotor 1 according to the present
embodiment. FIG. 2 is a partially enlarged view of FIG. 1. The
motor is a reluctance motor, for example.
[0019] The rotor core 1a is cylindrical, and at the center of the
rotor core 1a, a shaft hole 20 is provided, through which a shaft
(not shown) is inserted. The rotor core 1a is configured by
stacking many thin electromagnetic steel plates that are magnetic
materials with a thickness of approximately 0.1 to 1 millimeter.
The rotor 1 is rotatably arranged on the inside of a ring-shaped
stator (not shown).
[0020] In an outer peripheral portion of the rotor core 1a, a
plurality of magnet insertion holes 2 and 3 (for example, six holes
in an example of FIG. 1) are provided in a circumferential
direction, for example at equal intervals. Each of the magnet
insertion holes 2 and each of the magnet insertion holes 3 are
arrayed in two layers, for example, in the same radial direction.
The magnet insertion hole 2 is provided on the outer peripheral
side, while the magnet insertion hole 3 is provided on the inner
peripheral side. The magnet insertion holes 2 and 3 are arrayed so
as to be convex from the outer peripheral side toward the inner
peripheral side (that is, toward the center of the rotor).
Specifically, the magnet insertion holes 2 and 3 have substantially
a dish shape in cross section. In the rotor 1, a magnetic pole is
formed for each of the two layers of the magnet insertion holes 2
and 3 that are arrayed in the radial direction.
[0021] The magnet insertion hole 2 arranged on the outermost
peripheral side is constituted by including a main portion 2a that
extends with a constant width T1 in a direction substantially
perpendicular to the array direction of the magnet insertion holes
2 and 3 (in the same radial direction) and by including respective
end portions 2b that communication with both sides of the main
portion 2a and that extend with a constant width T1 toward the
outer peripheral side at an obtuse angle with respect to the
extending direction of the main portion 2a. The respective end
portions 2b are formed symmetrically with respect to the main
portion 2a.
[0022] The magnet insertion hole 3 arranged on the innermost
peripheral side is constituted by including a main portion 3a that
extends with a constant width T2 in a direction substantially
perpendicular to the array direction of the magnet insertion holes
2 and 3 (in the same radial direction) and by including respective
end portions 3b that communicate with both sides of the main
portion 3a, and that extend toward the outer peripheral side at an
obtuse angle with respect to the extending direction of the main
portion 3a. The respective end portions 3b are formed symmetrically
with respect to the main portion 3a.
[0023] The magnet insertion holes 2 and 3 are arranged
substantially parallel to each other. The magnet insertion hole 3
is longer than the magnet insertion hole 2 arranged on the outer
peripheral side in both the longitudinal direction and the short
direction, in which T2>T1 is established, for example (FIG. 2).
Opposed end portions 3b of the adjacent magnet insertion holes 3
are arranged between the magnet insertion holes 2 adjacent to each
other in the circumferential direction.
[0024] Next, the shape of the end portion 3b of the magnet
insertion hole 3 is explained. As shown in FIG. 2, the width of the
end portion 3b gradually becomes larger from the outer peripheral
side toward the inner peripheral side. Specifically, the width of
the end portion 3b is set to gradually become larger toward the
center of the rotor such that a width t of an iron core portion 10
that serves as a bridge portion between the opposed end portions 3b
is constant in the radial direction. In the example shown in FIG.
2, the width of the end portion 3b is T2 on the outermost
peripheral side, and it gradually becomes larger toward the center
of the rotor.
[0025] FIG. 3 is a plan view of a configuration of the rotor 1
according to the present embodiment. FIG. 4 is a partially enlarged
view of FIG. 3. As shown in FIGS. 3 and 4, a flat-shaped permanent
magnet 4 is inserted into the magnet insertion hole 2, and a
flat-shaped permanent magnet 5 is inserted into the magnet
insertion hole 3. A set of the permanent magnets 4 and 5
constitutes one magnetic pole of the rotor 1. In the example shown
in FIG. 3, the rotor 1 has six magnetic poles.
[0026] As shown in FIGS. 1 to 4, the thickness of the permanent
magnet 4 (the width of the permanent magnet 4 in the radial
direction) is substantially equal to T1. The permanent magnet 4 is
arranged in the magnet insertion hole 2 from the main portion 2a to
the end portions 2b. A gap is formed in a part of each of the end
portions 2b. The thickness of the permanent magnet 5 (the width of
the permanent magnet 5 in the radial direction) is substantially
equal to T2. The permanent magnet 5 is arranged in the magnet
insertion hole 3 from the main portion 3a to the end portions 3b. A
gap is formed in a part of each of the end portions 3b. An iron
core portion 6 is provided between the magnet insertion holes 2 and
3, and it is used for the magnetic flux, generated by the permanent
magnets 4 and 5, to pass through.
[0027] The permanent magnets 4 and 5 are magnetized such that the N
pole and the S pole are arranged alternately in the radial
direction. That is, the permanent magnets 4 and 5 that constitute
one magnetic pole are arranged so as to generate magnetic fluxes in
the same direction as each other. Further, the permanent magnets 4
and 5 are arranged such that adjacent magnetic poles have opposite
polarities to each other. In FIG. 4, two pairs of the permanent
magnets 4 and 5 are shown. In one of the pairs, the arrow
represents the direction of the N pole, while in the other pair,
the arrow represents the direction of the S pole.
[0028] Regarding the permanent magnets 4 and 5, for the permanent
magnet 4, a rare-earth magnet can be used, and for the permanent
magnet 5, a ferrite magnet can be used, for example. That is, the
rare-earth magnet is inserted into the magnet insertion hole 2
arranged on the outermost peripheral side, and the ferrite magnet
is inserted into the magnet insertion hole 3 arranged on the
innermost peripheral side.
[0029] In the above explanations, magnet insertion holes that
constitute each magnetic pole are formed into two layers, for
example. However, the magnet insertion holes can be formed into
three or more layers, and three or more permanent magnets can be
arrayed for each magnetic pole. In this case, at least the magnet
insertion hole arranged on the innermost peripheral side can have
the same shape as the magnet insertion hole 3, and the magnet
insertion hole arranged on the outermost peripheral side can have
the same shape as the magnet insertion hole 2. A ferrite magnet can
be inserted into the magnet insertion hole arranged on the
innermost peripheral side, and a rare-earth magnet can be inserted
in the magnet insertion hole arranged on the outermost peripheral
side. Further, the width of the main portion of the magnet
insertion hole arranged on the innermost peripheral side is made
larger than the width of the main portion of the magnet insertion
hole arranged on the outermost peripheral side, in order that the
thickness of the rare-earth magnet arranged on the outermost
peripheral side can be made smaller than the thickness of the
ferrite magnet arranged on the innermost peripheral side. A magnet
insertion hole on a middle layer other than the layer on the
outermost peripheral side and the layer on the innermost peripheral
side can have the same shape as the magnet insertion hole 2 or the
magnet insertion hole 3. In this case, the magnet insertion hole
with the same shape as the magnet insertion hole 2 can be arranged
on the outer peripheral side, and the magnet insertion hole with
the same shape as the magnet insertion hole 3 can be arranged on
the inner peripheral side, for example.
[0030] Next, an operation of the present embodiment is explained.
It is necessary for a reluctance motor to use reluctance torque in
order to obtain a high output. Reluctance torque is explained below
with reference to FIGS. 5 to 8. FIG. 5 is a plan view of a
configuration of a rotor 100 according to a comparative example.
FIG. 6 is a partially enlarged view of FIG. 5, and depicts a
magnetic path. FIG. 7 is a partially enlarged view of FIG. 5, and
depicts the width of iron core (hereinafter may be referred to just
as "iron-core width") between magnet insertion holes 103 adjacent
to each other. FIG. 8 is a partially enlarged view of FIG. 5 and it
explains the relation between the shape of the magnet insertion
hole 103 and the reluctance torque.
[0031] The rotor 100 includes a rotor core 100a in which a shaft
hole 120 is provided at its center. In an outer peripheral portion
of the rotor core 100a, a plurality of magnet insertion holes 102
and 103 (for example, six holes in an example of FIG. 5) are
provided in the circumferential direction, for example at equal
intervals, and each of the magnet insertion holes 102 and each of
the magnet insertion holes 103 are arrayed into two layers, for
example, in the same radial direction. The magnet insertion hole
102 is provided on the outer peripheral side, while the magnet
insertion hole 103 is provided on the inner peripheral side. In the
rotor 100, a magnetic pole is formed for each of the two layers of
the magnet insertion holes 102 and 103 that are arrayed in the
radial direction. The magnet insertion holes 102 and 103 have the
same shape as the magnet insertion hole 2 in FIGS. 1 to 4, except
for the size. That is, in this comparative example, the width of
the magnet insertion hole 103 is constant.
[0032] The magnet insertion hole 103 is longer than the magnet
insertion hole 102 in both the longitudinal direction and the short
direction. Flat-shaped permanent magnets 104 and 105 are inserted
respectively in the magnet insertion holes 102 and 103.
[0033] The magnet insertion holes 102 and 103 are filled with air
except for a portion in which the permanent magnets 104 and 105 are
inserted. Therefore, in the rotor core 100a, a direction in which a
magnetic flux easily passes through (a d-axis direction) and a
direction in which a magnetic flux hardly passes through (a q-axis
direction) are provided (FIG. 6).
[0034] The torque .tau. of the reluctance motor (the reluctance
torque) is given as follows, where P represents the number of pairs
of poles, Ld represents a d-axis inductance, Lq represents a q-axis
inductance, id represents a d-axis current, and iq represents a
q-axis current.
.tau.=P.times.(Ld-Lq).times.id.times.iq
Therefore, to increase the torque .tau., it is important to make Ld
large and make Lq small. The rotor needs to have a shape such that
the magnetic flux in the d-axis direction easily passes through in
order to make Ld large, and a magnetic flux in the q-axis direction
hardly passes through in order to make Lq small. While in the
comparative example, the iron-core width between the magnet
insertion holes 102 and 103 is constant, the iron-core width
between the magnet insertion holes 103 adjacent to each other is
the narrowest (a width t') on the outermost periphery, and it
becomes larger toward the inner peripheral side (FIG. 7).
[0035] In this case, between the magnet insertion holes 103
adjacent to each other, the magnetic flux in the d-axis direction,
which flows into or flows out of the rotor 100, is determined by
the narrowest part of the iron-core width between the adjacent
magnet insertion holes 103, that is, determined by the width t' on
the outermost periphery. Therefore, an area D shown by hatching in
FIG. 8 is an unnecessary iron-core part for the magnetic flux to
pass through.
[0036] Accordingly, by forming a gap in the area D, it is possible
to make Lq small while Ld is kept constant. This increases the
reluctance torque, and thus it can be expected to obtain a high
output from the motor. Therefore, in the present embodiment, a
portion corresponding to the area D is provided in the magnet
insertion hole 3. As shown in FIG. 8, when the area D is formed as
a part of a magnet insertion hole, the width (the width in a
direction perpendicular to the magnet array direction) of an
insertable flat-shaped permanent magnet (for example, a ferrite
magnet) is changed from L1 to L2 (L2>L1). Because it is possible
to insert a larger-width permanent magnet, a larger magnetic force
can be obtained.
[0037] In the present embodiment, in order to use a magnetic torque
in addition to the above reluctance torque, a rare-earth magnet is
inserted into the magnet insertion hole 2, and a ferrite magnet is
inserted into the magnet insertion hole 3, for example (FIGS. 3 and
4). With this configuration, it is possible to use the magnetic
force of the ferrite magnet as an auxiliary force in addition to
the large magnetic force of the rare-earth magnet. If rare-earth
magnets are inserted into both the magnet insertion holes 2 and 3,
it is possible to further increase the magnetic force. However,
this is not preferable because using a large amount of rare-earth
material increases costs.
[0038] A ferrite magnet has a smaller magnetic coercive force than
a rare-earth magnet. When a diamagnetic field from a stator becomes
large, there is a possibility of causing demagnetization of the
ferrite magnet. Therefore, it is preferable that the thickness of
the ferrite magnet is made larger than that of the rare-earth
magnet (T1<T2).
[0039] In the present embodiment, the rotor includes a rotor iron
core in which multi-layered magnet insertion holes that are arrayed
in a radial direction so as to be convex toward the inner
peripheral side are provided for each magnetic pole, and in which
the multi-layered magnet insertion holes are arranged in a
circumferential direction according to the number of magnetic
poles, and includes flat-shaped permanent magnets, each of which is
inserted into the respective magnet insertion holes, wherein the
magnet insertion holes, which are arranged on the innermost
peripheral side and adjacent to each other in a circumferential
direction, are provided in such a manner that the width thereof is
set to gradually become larger toward the inner peripheral side so
that the iron-core width between the magnet insertion holes in the
circumferential direction is constant in a radial direction.
[0040] Therefore, the reluctance torque can be increased, and a
high output is obtained from a motor. Further, the width of the
flat-shaped permanent magnet to be inserted can be made large, and
it is possible to obtain a large magnetic force and achieve high
efficiency.
[0041] In the present embodiment, among the multi-layered magnet
insertion holes that constitute each magnetic pole, at least a
rare-earth magnet is inserted into the magnet insertion hole on the
outermost peripheral side, and a ferrite magnet is inserted into
the magnet insertion hole on the innermost peripheral side.
Therefore, in addition to the magnetic force of the rare-earth
magnet on the outermost peripheral side, the magnetic force of the
ferrite magnet on the innermost peripheral side is used as an
auxiliary force, and accordingly the amount of rare-earth magnet to
be used can be reduced, and it is possible to obtain a large
magnetic force and achieve high efficiency.
[0042] In the present embodiment, the width (the thickness) of the
ferrite magnet in a radial direction, which is inserted into the
magnet insertion hole on the innermost peripheral side, is larger
than the width of the rare-earth magnet that is inserted into the
magnet insertion hole on the outermost peripheral side. As
described above, a ferrite magnet, which has a smaller magnetic
coercive force than that of a rare-earth magnet, has a large
thickness so as to be strengthened against demagnetization, and
therefore a high-quality motor can be provided.
INDUSTRIAL APPLICABILITY
[0043] As described above, the present invention can be suitably
applied to a reluctance motor, for example.
* * * * *